Monday, January 29, 2007

Necessity is the mother of all inventions

Who ever said it, couldn't have been more right. I find myself building utilities and applications everytime I don't find the right one :) .. During the past few days, I built a similar utility plugin and I thought I might as well share it with the rest of the world.

A little background... I work on a myriad set of applications and technologies, and this requires me to keep doing a lot of activities on different applications parallely. So off-late I have been working on providing a JSF component that pulls in a user's presence information from a backend RTC server. In this case the backend happens to be Microsoft's Live Communication Server. As you might have guessed, I have a .NET component that is doing all the talking with the LCS instance and this component exposes its features as a set of WebServices which are then consumed by the Java layer and published to the application via a JSF component. No points for anyone guessing that this can be a mess to handle all alone :-p

Everytime I need to perform some quick and dirty work, Netbeans is the IDE of choice. One day I was trying out something on similar lines, I needed to import only a subset of the Java classes into a project. And I knew that the IDE did not present me a feature where I could pick and choose. The only option I had was to copy the files over manually outside the IDE and then delete those that I didn't require. That can be quite painful at times! I dearly wished I had an option where I could look at the files being imported in a tree structure, where I could just (un)select the files I wanted.... So I built myself one of those things :-D ... Here is a screenshot of the module in action..

As a part of my work, I ran into a hard-to-trace, intermittent bug that would cause the .NET layer to crash once in a while. One rather good thing that I did do was use Log4Net's logger within the entire .NET code. So I whipped out my IDE of choice, built the test-bed and began the debugging. Everything was fine and going smooth, except that I had to switch between two applications to keep monitoring the output. That is when I though... "How I wish I had a module that could tail this file and show me the data within the IDE itself!". I took a measure of the expected effort, realized it wasn't much, went ahead and built myself exactly what I wanted. Check it out in action....

Like what you see? Get it here.

Thats all for now, later!

Saturday, January 20, 2007

Java6: GroupLayout and a small gotcha

The new layout manager, GroupLayout, which is part of the JavaSE 6 bundle is great and coupled with Netbeans' Matisse component, makes a killer combination. Today I would like to talk about an issue that I ran into and hopefully would be able to help others running into the same issue.

Anyways, if you try hand-coding this layout for your components, there is a rather subtle thing to remember. In Java 5, if you wanted to add a component to a container like JPanel, you would do something like:

JPanel jp = new JPanel();
JButton button = new JButton(...);

The key point to notice is that you would explicitly get hold of the content pane and then add the component to it. Now with Java 6, the good old ways of adding a component directly to the parent are back (which internally ensures that the component is added to the content pane), i.e., the same example above could be simplified as:


All this fine and nice. Now when using GroupLayout, the code might look as follows (in Java 5):

GroupLayout layout = new GroupLayout(jp.getContentPane());
... // add the component to the layout

Since I was working with Java 6, I decided to use the simplified notation and did the following:

GroupLayout layout = new GroupLayout(jp);
... // add the component to the layout

And was I in for a shock when I ran the code !!! I kept seeing the following stack trace on my screen :-O

Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException:
GroupLayout can only be used with one Container at a time
at javax.swing.GroupLayout.checkParent(
at javax.swing.GroupLayout.invalidateLayout(

It took me a while (which involved going through the source-code of GroupLayout) to figure out that the problem was actually with the way I am initializing the damn GroupLayout instance! The layout instance considers that it is being applied to the container ( JPanel in our case) whereas, the setLayout() method delegates the call to the content pane. And GroupLayout does a check to see that the host and owner are the same, if not, it throws a rather undecipherable exception like the one above. The key to getting it run was just simply to pass the content pane to the constructor of the GroupLayout instance.

GroupLayout layout = new GroupLayout(jp.getContentPane());
... // add the component to the layout

This experiment sure was good learning, but it would have been great if the implementation of GroupLayout threw a more meaningful exception stating the obvious rather than leaving us to figure out the obscure bits!

Thats all for now.